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Date:   Mon, 27 Apr 2020 20:26:33 +0530
From:   Calvin Johnson <calvin.johnson@oss.nxp.com>
To:     Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc:     linux.cj@gmail.com, Jeremy Linton <jeremy.linton@arm.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Cristi Sovaiala <cristian.sovaiala@nxp.com>,
        Florin Laurentiu Chiculita <florinlaurentiu.chiculita@nxp.com>,
        Ioana Ciornei <ioana.ciornei@nxp.com>,
        Madalin Bucur <madalin.bucur@oss.nxp.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
        Diana Madalina Craciun <diana.craciun@nxp.com>,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        linux-acpi@vger.kernel.org, Marcin Wojtas <mw@semihalf.com>,
        Makarand Pawagi <makarand.pawagi@nxp.com>,
        "Rajesh V . Bikkina" <rajesh.bikkina@nxp.com>,
        Varun Sethi <V.Sethi@nxp.com>, linux-kernel@vger.kernel.org,
        Pankaj Bansal <pankaj.bansal@nxp.com>,
        "David S. Miller" <davem@davemloft.net>,
        Heiner Kallweit <hkallweit1@gmail.com>
Subject: Re: [net-next PATCH v2 0/3] Introduce new APIs to support phylink
 and phy layers
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On Mon, Apr 27, 2020 at 03:48:07PM +0100, Russell King - ARM Linux admin wrote:
> On Mon, Apr 27, 2020 at 08:02:38PM +0530, Calvin Johnson wrote:
> > On Mon, Apr 27, 2020 at 02:58:20PM +0100, Russell King - ARM Linux admin wrote:
> > > On Mon, Apr 27, 2020 at 06:54:06PM +0530, Calvin Johnson wrote:
> > > > Following functions are defined:
> > > >   phylink_fwnode_phy_connect()
> > > >   phylink_device_phy_connect()
> > > >   fwnode_phy_find_device()
> > > >   device_phy_find_device()
> > > >   fwnode_get_phy_node()
> > > > 
> > > > First two help in connecting phy to phylink instance.
> > > > Next two help in finding a phy on a mdiobus.
> > > > Last one helps in getting phy_node from a fwnode.
> > > > 
> > > > Changes in v2:
> > > >   move phy code from base/property.c to net/phy/phy_device.c
> > > >   replace acpi & of code to get phy-handle with fwnode_find_reference
> > > >   replace of_ and acpi_ code with generic fwnode to get phy-handle.
> > > > 
> > > > Calvin Johnson (3):
> > > >   device property: Introduce phy related fwnode functions
> > > >   net: phy: alphabetically sort header includes
> > > >   phylink: Introduce phylink_fwnode_phy_connect()
> > > 
> > > Thanks for this, but there's more work that needs to be done here.  I
> > > also think that we must have an ack from ACPI people before this can be
> > > accepted - you are in effect proposing a new way for representing PHYs
> > > in ACPI.
> > 
> > Thanks for your review.
> > 
> > Agree that we need an ack from ACPI people.
> > However, I don't think it is a completely new way as similar acpi approach to
> > get phy-handle is already in place.
> > Please see this:
> > https://elixir.bootlin.com/linux/v5.7-rc3/source/drivers/net/ethernet/apm/xgene/xgene_enet_hw.c#L832
> 
> That was added by:
> 
> commit 8089a96f601bdfe3e1b41d14bb703aafaf1b8f34
> Author: Iyappan Subramanian <isubramanian@apm.com>
> Date:   Mon Jul 25 17:12:41 2016 -0700
> 
>     drivers: net: xgene: Add backward compatibility
> 
>     This patch adds xgene_enet_check_phy_hanlde() function that checks whether
>     MDIO driver is probed successfully and sets pdata->mdio_driver to true.
>     If MDIO driver is not probed, ethernet driver falls back to backward
>     compatibility mode.
> 
>     Since enum xgene_enet_cmd is used by MDIO driver, removing this from
>     ethernet driver.
> 
>     Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
>     Tested-by: Fushen Chen <fchen@apm.com>
>     Tested-by: Toan Le <toanle@apm.com>
>     Signed-off-by: David S. Miller <davem@davemloft.net>
> 
> The commit message says nothing about adding ACPI stuff, and searching
> the 'net for the posting of this patch seems to suggest that it wasn't
> obviously copied to any ACPI people:
> 
>     https://lists.openwall.net/netdev/2016/07/26/11
> 
> Annoyingly, searching for:
> 
>     "drivers: net: xgene: Add backward compatibility" site:lore.kernel.org
> 
> doesn't find it on lore, so can't get the full headers and therefore
> addresses.
> 
> So, yes, there's another driver using it, but the ACPI folk probably
> never got a look-in on that instance.  Even if they had been copied,
> the patch description is probably sufficiently poor that they wouldn't
> have read the patch.
> 
> I'd say there's questions over whether ACPI people will find this an
> acceptable approach.
> 
> Given that your patch moves this from one driver to a subsystem thing,
> it needs to be ratified by ACPI people, because it's effectively
> becoming a standardised way to represent a PHY in ACPI.
> 
Thanks for digging deep. Makes sense to me.
Will wait for ACPI response.

Regards
Calvin